Process for producing foam slabs of rectangular cross-section

Abstract

In the continuous production of rectangular foam slabs wherein a foamable reaction mixture is foamed on a forwardly moving floor web and lateral confining webs, and in which a cover web is applied during the foaming process to the surface of the rising foam, the improvement which comprises supplying said cover web from a supply to the surface under controllable tension, thereby exercising a controllable pressure on the surface of the rising foam, removing the cover web from the foam surface beyond the point at which the rising mixture has substantially reached its maximum height and passing the web rearwardly and then forwardly to serve as the floor web for receiving further foamable mixture. Advantageously the cover web is heated before application to the foaming mixture, it is pressed against the foam surface with a pressure of about 2 to 4 kilograms per square meter, it is removed from the foam surface about 2 to 4 meters downstream of where the foam mixture has reached its maximum height, and it is dried before it becomes the floor web. A corresponding apparatus is provided, with vertically adjustable transversely extending horizontal control members governing the locations where the cover web contacts and leaves the foam surface. The control members may be as long as the cover web is wide or they may be from about 15 to 25 cm shorter.

What is claimed is: 
     
       1. In the continuous production of rectangular foam slabs wherein a foamable reaction mixture is foamed on a forwardly moving floor web and lateral confining webs, and in which a cover web is applied during the foaming process to the surface of the rising foam, the improvement which comprises supplying said cover web from a supply upon the still liquid foam surface, subjecting the cover web to an adjustable tensile stress, thereby exercising a pressure of about 1 to 6 Kg/m 2  on the surface of the rising foam, removing the cover web from the foam surface beyond the point at which the rising mixture has substantially reached its maximum height, and passing the web rearwardly and then forwardly to serve as the floor web for receiving further foamable mixture. 
     
     
       2. The method of claim 1, wherein the cover web is removed from the foam surface about 1 to 6 meters downstream of where the foam mixture has reached its maximum height. 
     
     
       3. The method of claim 1, wherein the cover web is removed from the foam surface shortly downstream of where the foam has passed from the plastic to the solid state or when most of the gas formed in the reaction begins to escape. 
     
     
       4. The method of claim 1, wherein the web comprises paper. 
     
     
       5. The method of claim 1, wherein the web comprises plastic. 
     
     
       6. The method of claim 1, wherein the cover web is pressed against the foam surface with a pressure of about 2 to 4 kilograms per square meter. 
     
     
       7. The method of claim 1, wherein the cover web is heated before application to the foaming mixture. 
     
     
       8. The method of claim 7, wherein the cover web is pressed against the foam surface with a pressure of about 2 to 4 kilograms per square meter, the cover web is removed from the foam surface about 2 to 4 meters downstream of where the foam mixture has reached its maximum height, and the cover web is dried before it becomes the floor web.